1. Field of Invention
The present invention relates to a dialysis liquid circuit with conduits for conducting dialysis liquid and with means for detecting air in the dialysis liquid.
2. Description of the Prior Art
The presence of air in a dialysis liquid conducted in a dialysis liquid circuit is undesirable in several respects. On the one hand, air bubbles can impede the measurement of the concentration of ingredients of the dialysis liquid, as is known from WO 96/04401. According to this document, it therefore is proposed to degas the dialysis liquid before measuring the concentration. On the other hand, air bubbles are disadvantageous for correctly balancing the dialysis liquids entering the dialyser and emerging from the same, since the commonly used balancing means employ a degassed dialysis liquid.
By level measurement in the air separation chamber, it is furthermore known to detect large amounts of air in the system. However, this does not provide a fast and reliable possibility for monitoring the dialysis liquid circuit for leakages.
For detecting leakages, leakage sensors are known which can, however, only be employed when there is a leakage of liquid. From the prior art it is furthermore known to detect leakages in the negative pressure region of the dialysis liquid circuit. For this purpose, the liquid circuit is stopped upon build-up of a negative pressure, the point to be examined is sealed and the course of pressure in time is measured. When the negative pressure is reduced, this is an indication for the penetration of air into the dialysis liquid circuit and hence for a leakage. According to this known method, pressure sensors and valves are necessary for sealing and limiting the region to be examined. A further disadvantage results from the fact that the liquid circulation must be stopped for the examination for leakages.